Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
  • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
  • B23K35/36—Selection of non-metallic compositions, e.g. coatings, fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
  • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
  • B23K35/36—Selection of non-metallic compositions, e.g. coatings, fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest
  • B23K35/368—Selection of non-metallic compositions of core materials either alone or conjoint with selection of soldering or welding materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
  • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
  • B23K35/36—Selection of non-metallic compositions, e.g. coatings, fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest
  • B23K35/3601—Selection of non-metallic compositions, e.g. coatings, fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest with inorganic compounds as principal constituents
  • B23K35/3608—Titania or titanates

Definitions

• the present invention relates to a flux cored wire for gas shielded arc welding of high tensile strength steel of 80 kgf/mm 2 grade, and more particularly, to a flux cored wire for gas shielded arc welding of high tensile strength steel of 80 kgf/mm 2 grade, which exhibits improved workability and low temperature impact toughness resulting from filling a titania based flux in the wire.
• titania based flux cored wires can be substituted for the basic flux cored wires.
• a problem may occur that although added TiO 2 s along with other oxides produce slag and the resultant slag covers the surface of a bead, only a few of the TiO 2 s are present in an interior of weld metal as a non-metallic inclusion, making it possible to increase the amount of oxygen in the weld metal, whereby the toughness of the weld metal is lowered.
• the present invention has been made in view of the above problems, and it is an object of the present invention to provide a flux cored wire for gas shielded arc welding of high tensile strength steel, which is excellent in workability and low temperature impact toughness property and has more than 80 kgf/mm 2 of high tensile strength.
• the above object can be accomplished by the provision of a flux cored wire for gas shielded arc welding, characterized in that the flux essentially consists of, with respect to the total weight of the wire:
• a flux cored wire which has excellent workability and a Charpy V-notched impact property of more than 27J at 0, as well as maintains a high tensile strength of more than 80 kgf/mm 2 grade.
• the present invention employs a titania based flux instead of a basic flux. Further, Ti or TiO 2 oxide and Si or SiO 2 oxide are appropriately used. Metal Mg and Al or alloy including them is also used in combination with conventional manganese metal, silicon metal or ferroalloy thereof as a deoxidizing agent, in order to prevent non-metallic inclusions from remaining in an interior of weld metal.
• the flux may contain an alloying agent as an additive.
• deoxidizing agents have been used to obtain stronger welded portions by removing impurities and gases such as oxygen, nitrogen, hydrogen, etc. in weld metal during welding. Hitherto, Fe—Mn, Fe—Si, Fe—Ti or the like have been predominantly used for this purpose.
• the present inventors discovered the fact that when Mg and Al metal powder or an alloying agent containing them was contained in the flux and the sum of Si, Mg and Al was set to 0.5-1.5% of the total weight of the wire, it was possible to stabilize arc and to make the transfer of metal droplets fine, simultaneously with maintaining a sufficient deoxidizing effect.
• Mn is a component for providing a sufficient deoxidizing effect of weld metal, and, at the same time, enhancing the toughness and strength thereof.
• the content of Mn is set to 1.5-2.7% of the total weight of the wire.
• Mn can be added in the form of metal Mn alone or an Mn alloy such as Fe—Mn, Fe—Si—Mn, etc., provided that the requirement for the content of Mn is satisfied.
• Mg and Al are components for making the shape of a bead uniform by controlling the solidification rate of weld metal during a horizontal or vertical welding.
• Mn/(Mg+Al) is less than 3.5, the solidification of slag is facilitated, so that a uniform shape of a bead cannot be obtained. If it exceeds 5.0, the solidification of slag is too low, so that a poor distribution of a bead occurs and the amount of spatter and the amount of fumes increase.
• the value of Mn/(Mg+Al) is set to 3.5-5.0.
• Mg and Al can be added in either the form of metal powder or an alloy such as Fe—Al and Mg—Al, provided that all the requirements for the sum of Si, Mg and Al, and the value of Mn/(Mg+Al) are satisfied.
• TiO 2 and SiO 2 serve as a slag forming agent. In addition, they improve slag fluidity and arc stability.
• the slag fluidity and viscosity are low, so that when used on a medium or high current condition (in the case of 1.2 mm ⁇ wire, the medium current is 240-280A, and the high current is 300-360A), it is likely to generate undercut in a horizontal fillet position, while increasing the amount of produced spatter and causing droop of a bead in a vertical upward position. Also, if the welding rate is faster, the amount of produced slag is insufficient and the covering property of a bead is poor, causing deterioration of the bead appearance.
• the contents of TiO 2 and SiO 2 are set to 2.5-9% and 0.5-2.0%, respectively.
• TiO 2 and SiO 2 can be added in either the form of Ti and Si powder or ferroalloy and oxide such as rutile, leucoxene, silica, feldspar, mica, etc., provided that the requirement for the contents of TiO 2 and SiO 2 is satisfied.
• Cr, Ni, Mo and Nb are components for improving the tensile strength and toughness of weld metal.
• the weld metal cannot obtain more than 80 kgf/mm 2 of tensile strength and toughness, whereas if it exceeds 2.5%, the tensile strength is too large, lowering the toughness. Therefore, it is preferred that the sum of two or more components selected from the group consisting of Cr, Ni, Mo and Nb is set to 1.0-2.5% of the total weight of the wire.
• a flux is composed of chemical components according to the composition ratio shown in Table 2, main components of the flux follow the composition ratio shown in Table 3.
• the weight % in Table 3 is based on the total weight of the wire.
• Table 4 describes the welding conditions of the flux cored wires manufactured according to respective composition ratios shown in Table 2 and Table 3. The results of welding tests are presented in Table 5.
• TABLE 4 Section Welding conditions Test plate material Rolled steels for welding structures SM490A Test plate material thickness 12 mm, width 100 mm, length 300 mm dimensions Welding position Horizontal fillet position Vertical upward position Welding current 340 A 240 A Welding voltage 32 V 26 V Welding speed 40 cm/min — Shield gas 100% CO 2 Shield gas flow rate 20 ⁇ /min
• test specimens were manufactured according to the procedures of AWS standard under the welding conditions shown in Table 6.
• Table 7 shows the evaluation results of the welded metal under the welding conditions shown in Table 6.
• TABLE 6 Section Welding conditions Test plate steels Rolled steels for welding structures SM490A Test plate dimensions Thickness 19 mm, width 150 mm, length 300 mm Groove angle 45° Root space 12 mm Number of passes and layers 17 passes 6 layers The temperature between layers 150° C. Shield gas 100% CO 2 Welding current 260 A Welding voltage 32 V
• the flux cored wires for gas shielded arc welding in accordance with the present invention when optimizing the chemical components and their proportion of the flux, exhibit good welding workability in all welding positions, ensuring an improvement in the efficiency of welding work, and maintain high tensile strength and impact absorption energy, ensuring stability of welded structures.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Nonmetallic Welding Materials (AREA)
• Arc Welding In General (AREA)

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• 2001
  • 2001-05-28 KR KR10-2001-0029473A patent/KR100436489B1/ko active IP Right Grant
• 2002
  • 2002-05-20 JP JP2002144870A patent/JP2003033895A/ja active Pending
  • 2002-05-21 CN CNB021200440A patent/CN1240516C/zh not_active Expired - Lifetime
  • 2002-05-24 US US10/153,894 patent/US20030015257A1/en not_active Abandoned

Patent Citations (7)

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